How to fix Error: 'main' field in package.json is missing or points to non-existent file in Node.js

Check your package.json and confirm the file exists at the specified path:

{
  "name": "my-package",
  "main": "dist/index.js"  // Check this file exists
}

Navigate to your package directory and verify:

ls -la dist/index.js
# or on Windows
dir dist\index.js

If the file doesn't exist, you need to either create it or update the 'main' field to point to the correct file.

If your package.json doesn't have a 'main' field, add it pointing to your entry file:

{
  "name": "my-package",
  "version": "1.0.0",
  "main": "index.js"  // Add this line
}

Common entry point locations:
- "main": "index.js" - For packages with source in root
- "main": "dist/index.js" - For TypeScript/compiled packages
- "main": "lib/index.js" - Another common convention
- "main": "src/index.js" - For source-only packages

If using TypeScript or a build tool, make sure the entry file is generated:

For TypeScript, check your tsconfig.json:

{
  "compilerOptions": {
    "outDir": "./dist"  // Must match 'main' path
  }
}

Run your build command:

npm run build
# or
tsc

Verify the output file exists:

ls -la dist/index.js

Ensure the entry file is included in your published package. Check the 'files' array in package.json:

{
  "name": "my-package",
  "main": "dist/index.js",
  "files": [
    "dist"  // Include the directory containing main file
  ]
}

Test locally before publishing:

npm pack
tar -tzf my-package-1.0.0.tgz

This shows exactly what files will be published. Verify your main entry file is included.

If you renamed or moved your entry file, update package.json to match:

Before:

{
  "main": "index.js"
}

After moving file to src/:

{
  "main": "src/index.js"
}

Remember: the path is relative to package.json, not an absolute path.

Before publishing, test that your package can be imported:

In your package directory:

npm link

In a test project:

npm link my-package

Try importing it:

// test.js
const myPackage = require('my-package');
// or
import myPackage from 'my-package';

Run the test:

node test.js

This confirms the 'main' field resolves correctly.